Abrasive ceramic matrix turbine blade tip and method for forming

Abstract

An abrasive coating suitable for forming an abrasive blade tip of a gas turbine engine. The coating is characterized as being capable of abrading a ceramic shroud at elevated temperatures during the in-service operation of the engine, and being resistant to oxidation and hot corrosion within the engine environment. The abrasive coating includes an MCrAl alloy layer, a ceramic layer overlying the alloy layer so as to form an outer surface of the abrasive coating, and abrasive particles dispersed between the alloy layer and the ceramic layer so that at least some of the abrasive particles are partially embedded in the alloy layer and also partially embedded in the ceramic layer. In addition, at least some of the abrasive particles project above the outer surface of the abrasive coating formed by the ceramic layer.

What is claimed is: 
     
       1. An abrasive coating on a substrate, the abrasive coating comprising; an MCrAl alloy layer on the substrate;   a ceramic layer of yttria-stabilized zirconia overlying the alloy layer so as to form an outer surface of the abrasive coating, and   abrasive particles dispersed between the alloy layer and the ceramic layer so that at least some of the abrasive particles are partially embedded in the alloy layer and partially embedded in the ceramic layer, at least some of the abrasive particles projecting beyond the outer surface of the abrasive coating formed by the ceramic layer.   
     
     
       2. The abrasive coating of claim 1, wherein the alloy layer consists essentially of, in weight percent, about 8 to about 12 percent chromium, about 5 to about 10 percent cobalt, about 5 to about 7 percent aluminum, about 2 to about 6 percent tantalum, about 2 to about 4 percent tungsten, about 1 to about 3 percent molybdenum, up to about 4 percent rhenium, up to about 2 percent titanium, up to about 1 percent hafnium, up to about 1 percent yttrium, up to about 1 percent niobium, up to about 0.07 percent carbon, up to about 0.03 percent zirconium, up to about 0.03 percent boron, with the balance being nickel and incidental impurities. 
     
     
       3. The abrasive coating of claim 1, wherein the alloy layer consists essentially of, in weight percent, about 14 to about 18 percent chromium, about 9.75 to about 11.45 percent cobalt, about 6.45 to about 6.95 percent aluminum, about 5.95 to about 6.55 percent tantalum, about 1.85 to about 2.35 percent rhenium, about 0.5 to about 1.75 percent hafnium, about 0.02 to about 0.11 percent carbon, about 0.006 to about 0.03 percent zirconium, up to about 1.1 percent silicon, up to about 0.01 percent boron, with the balance being nickel and incidental impurities. 
     
     
       4. The abrasive coating of claim 1, wherein abrasive particles are microcrystalline oxide particles. 
     
     
       5. The abrasive coating of claim 1, wherein the abrasive particles are sol-gel alumina particles. 
     
     
       6. The abrasive coating of claim 1, wherein an average of about 30 to about 60 volume percent of the abrasive particles is embedded in the alloy layer. 
     
     
       7. The abrasive coating of claim 6, wherein an average of about 60 to about 95 volume percent of the abrasive particles is embedded within the alloy and ceramic layers. 
     
     
       8. The abrasive coating of claim 1, wherein an average of about 60 to about 95 volume percent of the abrasive particles is embedded within the alloy and ceramic layers. 
     
     
       9. The abrasive coating of claim 1, wherein the substrate is a nickel superalloy turbine blade tip. 
     
     
       10. An abrasive coating on a nickel superalloy substrate, the abrasive coating comprising; an alloy layer on the substrate, the alloy layer consisting essentially of, in weight percent, about 14 to about 18 percent chromium, about 9.75 to about 11.45 percent cobalt, about 6.45 to about 6.95 percent aluminum, about 5.95 to about 6.55 percent tantalum, about 1.85 to about 2.35 percent rhenium, about 0.5 to about 1.75 percent hafnium, about 0.02 to about 0.11 percent carbon, about 0.006 to about 0.03 percent zirconium, up to about 1.1 percent silicon, up to about 0.01 percent boron, with the balance being nickel and incidental impurities;   a ceramic layer overlying the alloy layer so as to form an outer surface of the abrasive coating, the ceramic layer being yttria-stabilized zirconia; and   a single layer of microcrystalline oxide particles dispersed between the alloy layer and the ceramic layer so that about 30 to 60 volume percent of the particles is embedded in the alloy layer and so that about 60 to about 95 volume percent of the particles is embedded within the alloy and ceramic layers, such that at least some of the particles project above the outer surface of the abrasive coating formed by the ceramic layer.   
     
     
       11. The abrasive coating of claim 10, wherein the nickel superalloy substrate is a blade tip of a turbine blade. 
     
     
       12. A method for forming an abrasive coating on a substrate, the method comprising the steps of; depositing an MCrAl alloy on the substrate;   incorporating a dispersion of abrasive particles into the MCrAl alloy after an initial layer of the MCrAl alloy is formed, such that continued deposition of the MCrAl alloy causes the abrasive particles to be partially embedded therein; and   depositing a ceramic layer of yttria-stabilized zirconia on the MCrAl alloy so as to form an outer surface of the abrasive coating, the abrasive particles being partially embedded in the ceramic layer such that at least some of the abrasive particles project above the outer surface of the abrasive coating formed by the ceramic layer.   
     
     
       13. The method of claim 12, wherein the alloy layer consists essentially of, in weight percent, about 8 to about 12 percent chromium, about 5 to about 10 percent cobalt, about 5 to about 7 percent aluminum, about 2 to about 6 percent tantalum, about 2 to about 4 percent tungsten, about 1 to about 3 percent molybdenum, up to about 4 percent rhenium, up to about 2 percent titanium, up to about 1 percent hafnium, up to about 1 percent yttrium, up to about 1 percent niobium, up to about 0.07 percent carbon, up to about 0.03 percent zirconium, up to about 0.03 percent boron, with the balance being nickel and incidental impurities. 
     
     
       14. The method of claim 12, wherein the alloy layer consists essentially of, in weight percent, about 14 to about 18 percent chromium, about 9.75 to about 11.45 percent cobalt, about 6.45 to about 6.95 percent aluminum, about 5.95 to about 6.55 percent tantalum, about 1.85 to about 2.35 percent rhenium, about 0.5 to about 1.75 percent hafnium, about 0.02 to about 0.11 percent carbon, about 0.006 to about 0.03 percent zirconium, up to about 1.1 percent silicon, up to about 0.01 percent boron, with the balance being nickel and incidental impurities. 
     
     
       15. The method of claim 12, wherein the ceramic layer is deposited by a plasma spray or PVD technique. 
     
     
       16. The method of claim 13, wherein the abrasive particles are sol-gel alumina particles. 
     
     
       17. The method of claim 12, wherein an average of about 30 to about 60 volume percent of the abrasive particles is embedded in the alloy layer, and wherein an average of about 60 to about 95 volume percent of the abrasive particles is embedded within the alloy and ceramic layers. 
     
     
       18. The method of claim 12, wherein the MCrAl alloy is deposited by electroplating. 
     
     
       19. The method of claim 12, wherein the substrate is a nickel superalloy turbine blade tip.